Investigation of spectral phase fluctuations on the performance of an LPA-driven FEL*

Laser plasma accelerators (LPAs) have emerged as a promising alternative to classical accelerators for a variety of applications, due to their ability to produce high brightness beams and significantly higher accelerating gradients, allowing more compact designs for future light sources and colliders. However, the LPA mechanism comes with a unique set of challenges based on the nature of the interaction between the laser pulse and the plasma. In order to enable reliable operation of an LPA driven FEL, key parameters that drive the LPA interaction need to be closely monitored and controlled. A critical parameter for this interaction is the spectral phase, which determines the chirp and pulse length of the driving laser. We report on a diagnostic implemented in our experimental setup that allows full on-shot characterization of the spectral phase and amplitude of the amplified laser. This enables detailed investigations of the correlation between the spectral phase and LPA, as potentially the FEL performance.